Corn, like any other plant, needs to mature vegetatively before it can flower and set seed. Since the kernels on the ear are the plant's way of making seed, it's not likely the ears will begin to form until the stalks are old enough to support the process. Corn usually ripens about three weeks after the silks appear. In your gardening region you still have lots of summer weather left, so don't worry too much about the stalks forming ears. They will, and you'll be able to harvest near the end of the season.